Ractopamine HC1 and zilpaterol HC1, β-agonists recently approved for use in feedlot cattle to improve performance traits and carcass leanness, were examined for their effects on fecal shedding of Escherichia coli 0157:H7 in feedlot cattle. Fecal samples (n = 2,454) were obtained from four experiments (one ractopamine HC1, three zilpaterol HC1) over the course of a 3-year period, either by rectal palpation (ractopamine HC1 experiment) or from pen-floor fecal pats. Samples were cultured quantitatively and qualitatively for E. coli 0157:H7. No significant treatment differences were detected for fecal prevalence of E. coli 0157:H7 in the ractopamine HC1 experiment. Zilpaterol HC1 feeding had no effect (P > 0.20) on fecal shedding in the first or second experiments, with overall E. coli 0157:H7 prevalence relatively low (<7%). In the third zilpaterol HC1 experiment, the percentage of fecal samples that were E. coli 0157:H7 positive following qualitative culture was higher (P < 0.05) in the zilpaterol HC1 treatment (10.3%) than for the control (6.1%). The current research showed minimal effects of β-agonists on fecal shedding off. coli 0157:H7 and indicated that these compounds (fed immediately prior to slaughter) are not a cause for concern from a food safety standpoint.
|Number of pages||5|
|Journal||Journal of food protection|
|State||Published - Dec 2009|